Development of immunoassays for serum tartrate-resistant acid phosphatase isoform 5a

Tsu Yi Chao, Su Huei Lee, Mary M. Chen, David H. Neustadt, Uzma A. Chaudhry, Lung T. Yam, Anthony J. Janckila

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Background: Serum tartrate-resistant acid phosphatase (TRACP) consists of 2 structurally related isoforms, TRACP 5a and 5b. TRACP 5b is from bone-resorbing osteoclasts. TRACP 5a may be a macrophage product of inflammation. We used a novel antibody to TRACP 5a to standardize immunoassays for serum TRACP 5a activity and protein. Methods: Biotinylated anti-TRACP antibodies were used to immobilize serum TRACP isoforms. TRACP activity was measured using 4-nitrophenyl phosphate as substrate. TRACP 5a protein was measured with an independent peroxidase-conjugated anti-TRACP antibody. Immunoassays were standardized for linearity of serum dose response, sensitivity and precision. Reference ranges for TRACP 5a were established from serum of 50 healthy males and 50 healthy age-matched females. Serum TRACP 5a activity and protein were determined in 29 cases of rheumatoid arthritis. Results: Serum matrix interference in both TRACP 5a assays required dilution to 10% serum to approach linearity. Intra-assay and inter-assay CV% were <10%. Mean serum TRACP 5a activity and protein were significantly higher in healthy men than women. There was a slight, but significant age related increase in both serum TRACP 5a and 5b among females, but not males, from age 20 to 70 years. TRACP 5a activity was positively correlated to TRACP 5a protein in healthy sera. Neither TRACP 5a activity nor protein was correlated strongly to TRACP-5b activity. TRACP 5a protein was significantly increased in 8/29 RA sera, whereas TRACP 5a and 5b activities were not. TRACP 5a activity and protein were not significantly correlated in RA sera. Conclusions: Although TRACP 5a and 5b are related biosynthetically, their circulating levels in healthy humans were independent, suggesting differential regulation of expression. In chronic diseases, increased TRACP 5a may represent pathological processes of inflammation unrelated to bone metabolism.

Original languageEnglish
Pages (from-to)132-140
Number of pages9
JournalClinica Chimica Acta
Issue number1-2
Publication statusPublished - Sept 2005
Externally publishedYes


  • Acid phosphatase
  • Bone resorption
  • Immunoassay
  • Inflammation

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry
  • Biochemistry, medical


Dive into the research topics of 'Development of immunoassays for serum tartrate-resistant acid phosphatase isoform 5a'. Together they form a unique fingerprint.

Cite this